The preparation of methylamines of general formula (CH.sub.3).sub.n NH.sub.3-n and (CH.sub.3).sub.n NH.sub.2-n R occurs by the reactions depicted in equations (1) and (2). An example of such process is the preparation of monomethylamine from ammonia and synthesis gas as shown in equation (3). EQU NH.sub.3 +nCO+2nH.sub.2 .fwdarw.(CH.sub.3).sub.n NH.sub.3-n +nH.sub.2 O (1) EQU NH.sub.2 R+nCO+2nH.sub.2 .fwdarw.(CH.sub.3).sub.n NH.sub.2-n R+nH.sub.2 O (2) EQU NH.sub.3 +CO+2H.sub.2 .fwdarw.CH.sub.3 NH.sub.2 +H.sub.2 O (3)
Methylamines are presently produced by a continuous process with methanol and ammonia using an amorphous silica-alumina catalyst. Even at low methanol conversion efficiencies, such processes are unselective and generally tend to the production of excess trimethylamine over the mono and dimethylamines. Production of maximum amounts of the monomethylamine is achieved when equilibrium is reached at high methanol conversion. However, the relative amounts of the three amine species at equilibrium depend on the methanol to ammonia ratio in the reactant feed stream. At ratios of approximately 1:1 the product contains about 55% ammonia, 12% monomethylamine, 12% dimethylamine, and 22% trimethylamine, on a molar basis (Weigert, U.S. Pat. No. 4,254,061).
Other minerals have been utilized as catalysts for the formation of methylamines by the processes of equation (3). These alternative catalysts however, generally exhibit very poor activity and thus require the use of elevated temperatures resulting in undesirable selectivities. For example, the sodium mordenite of U.S. Pat. No. 4,254,061 describes a reaction of ammonia with methanol at 400.degree. C., 300 psig, and a 1.1 second contact time at 1 atm. These conditions yield a 24% alcohol conversion and a formation of 8.7.times.10.sup.-6 mol monomethylamine per kilogram of catalyst per hour with a selectivity of monomethylamine/dimethylamine/trimethylamine=86.7/9.3/4.0 mol%.
Various synthetic oxide catalysts containing transition metal ions have been utilized as catalysts for the formation of methylamines from synthesis gas and ammonia. U.S. Pat. No. 3,444,203 describes the reaction of NH.sub.3 /CO/H.sub.2 =1.3/1/2 over a ZnO/CuO/Cr.sub.2 O.sub.3 /Ferrochrome/Binder catalyst at 362.degree. C., 975 psig, and a 2.3 second contact time at one atmosphere which yields a 24% CO conversion (47% to amines and 51% to CO.sub.2) to produce 0.72 mol monomethylamine per liter of catalyst per hour. The amine selectivity in this process was monomethylamine/dimethylamine/trimethylamine=64/22/14 mol%, and small amounts of methanol and methane were formed as side-products. Increasing the ammonia to carbon monoxide ratio to 2.6, while maintaining the hydrogen to carbon monoxide ratio at 2:1 gave rise to the formation of 0.52 mol monomethylamine per liter of catalyst per hour with 100% selectivity. Over Zn/Ba/Fe/Al catalysts and Cu/Ba/Fe/Al catalysts, it has been shown that decreasing the ammonia to carbon monoxide ratio leads to the formation of N-alkyl-amines with mainly C.sub.4 -C.sub.9 alkyl groups on the amines but not methyl groups (U.S. Pat. No. 3,726,926).